Method of overwriting data in nonvolatile memory and a control apparatus used for the method

Abstract

In a nonvolatile memory such as flash memory where data is stored sector by sector, a method of overwriting a data sector is provided. The old data to be overwritten in a data sector along with its error detection code are initially saved to a backup region which is also in a non-volatile area. The old data in the data sector is then erased and new data along with its own error detection code are written into the same data sector where the old data was previously stored. When a power outage occurs during the overwrite process, error checking is performed to determine whether the data in the data sector is valid using the associated error detection code. Because the old data is saved in a non-volatile area, even if such unexpected power outage occurs during the overwrite process and the data in the data sector is determined to be invalid, at least the old data can be recovered from the non-volatile backup region which is not affected by the power outage.

Description

BACKGROUND OF THE INVENTIONa) Field of the InventionThe present invention relates to a method of overwriting nonvolatile memory data and a control apparatus used for the method. More specifically, the present invention relates to a method of overwriting data in such a way that data saved in nonvolatile memory is protected and a control apparatus is used for the method.b) Description of the Related ArtLately, flash memory capacity has increased dramatically along with an exponential improvement in useable lifetime in terms of the number of times data in flash memory can be overwritten. By these advances, flash memory serves not only as the conventional coding program storage (medium), being overwritten less frequently, but also as nonvolatile memory, being overwritten very frequently.Flash memory has a unique property that affects the overwriting method: when one wants to write the bit data “1” over “0”, one must first erase all data in a sector to which the data to be overwritten (i...

AI Technical Summary

Problems solved by technology

It is impossible to pin-pointedly erase data in a sector.

However, erasing flash memory often requires erasure of entire data in a sector at first, requiring relatively long process time (e.g. seconds) compared to other processes.

For this reason, an interruption of power supply, if it occurs unexpectedly between the erasure of data in flash memory and the completion of writing the post-overwrite data, interrupts control of flash memory, causing loss of data saved on RAM, volatile memory; one may be seriously concerned with irrevocable loss of very important data.

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